I put a Hawke 2-7X on my gamo silent cat (.177) and I'm all out of adjustment in the down direction. Tight groups if I hold over 3 dots at 50'...but I like crosshairs for my POA. And I can see the front sight in the scope, so I think something isn't right. I thought about taller rings, but it's almost like the scope isn't level. No such problem with the scope that came with the rifle, and I'm using the same rings for the Hawke...

If, as I suspect, you are shooting a break-barrel air rifle, you will be fighting the barrel "droop", which can be more than the internal elevation adjustment of your scope. You'll need a base that has elevation compensation built-in to it, like these:

I see 13 hits on their site for "droop" mounts, and 19 mentions of "droop" on their "Airgun Academy" blog: http://www.pyramydair.com/blog/ If you search there or in general for your rifle model and "barrel droop" you are bound to find solutions.

Re-reading your post, I see your air rifle is a Gamo Silent Cat, which is indeed a break-barrel model. Pyramydair sells those rifles, so give them a call and ask for a suitable droop-compensating mount.